1. Field of the Invention
The present invention is directed in general to magnetic resonance tomography as employed in medicine for examining patients. The present invention is thereby specifically directed to a magnetic resonance apparatus as well as to a method for the operation thereof wherein a pulse sequence known as a true-FISP pulse sequence is employed.
2. Description of the Prior Art
Magnetic resonance tomography is a tomographic method for medical diagnostics that is distinguished by a high contrast resolution capability. Due to its excellent ability to present soft tissue, magnetic resonance tomography has developed into a method that is far superior to X-ray computed tomography. Magnetic resonance tomography is currently based on the application of spin echo sequences and gradient echo sequences that enable an excellent image quality given measurement times on the order of minutes.
In the presentation of the tissue of a patient, however, artifacts occur that arise from the influence of the chemical shift at the boundary layers between fat and water. A “chemical shift” is the phenomenon that the resonant frequency shifts slightly in proportion to the field strength dependent on the type of chemical bond in which the excited nucleus participates. Due to their concentration in the human body, it is mainly hydrogen nuclei of free water and fat that contribute to the image. Their relative difference in resonant frequency amounts to about 3 ppm (parts per million). As a result thereof, a modulation of the signal intensity dependent on the echo time TE occurs given employment of steady state gradient echo sequences.
These artifacts must be avoided since they can lead to an incorrect diagnosis.